/*
 * Copyright © 2019-2023 Apple Inc. and the ServiceTalk project authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.servicetalk.http.netty;

import io.servicetalk.client.api.ConnectionFactoryFilter;
import io.servicetalk.concurrent.api.Single;
import io.servicetalk.http.api.FilterableStreamingHttpConnection;
import io.servicetalk.http.api.HttpExecutionContext;
import io.servicetalk.http.api.HttpProtocolVersion;
import io.servicetalk.http.api.StreamingHttpConnectionFilterFactory;
import io.servicetalk.http.api.StreamingHttpRequestResponseFactory;
import io.servicetalk.tcp.netty.internal.ReadOnlyTcpClientConfig;
import io.servicetalk.tcp.netty.internal.TcpClientChannelInitializer;
import io.servicetalk.tcp.netty.internal.TcpConnector;
import io.servicetalk.transport.api.ConnectionObserver;
import io.servicetalk.transport.api.ExecutionStrategy;
import io.servicetalk.transport.api.TransportObserver;

import io.netty.channel.Channel;

import java.util.function.Function;
import javax.annotation.Nullable;

import static io.servicetalk.concurrent.api.Single.failed;
import static io.servicetalk.http.netty.AlpnIds.HTTP_1_1;
import static io.servicetalk.http.netty.AlpnIds.HTTP_2;
import static io.servicetalk.http.netty.StreamingConnectionFactory.withSslConfigPeerHost;

final class AlpnLBHttpConnectionFactory<ResolvedAddress> extends AbstractLBHttpConnectionFactory<ResolvedAddress> {

    AlpnLBHttpConnectionFactory(
            final ReadOnlyHttpClientConfig config, final HttpExecutionContext executionContext,
            @Nullable final StreamingHttpConnectionFilterFactory connectionFilterFunction,
            final Function<HttpProtocolVersion, StreamingHttpRequestResponseFactory> reqRespFactoryFunc,
            final ExecutionStrategy connectStrategy,
            final ConnectionFactoryFilter<ResolvedAddress, FilterableStreamingHttpConnection> connectionFactoryFilter,
            final ProtocolBinding protocolBinding) {
        super(config, executionContext, reqRespFactoryFunc, connectStrategy, connectionFactoryFilter,
                connectionFilterFunction, protocolBinding);
        assert config.h1Config() != null && config.h2Config() != null;
    }

    @Override
    Single<FilterableStreamingHttpConnection> newFilterableConnection(
            final ResolvedAddress resolvedAddress, final TransportObserver observer) {
        // This state is read only, so safe to keep a copy across Subscribers
        final ReadOnlyTcpClientConfig tcpConfig = withSslConfigPeerHost(resolvedAddress, config.tcpConfig());
        // We disable auto read by default so we can handle stuff in the ConnectionFilter before we accept any content.
        // In case ALPN negotiates h2, h2 connection MUST enable auto read for its Channel.
        return TcpConnector.connect(null, resolvedAddress, tcpConfig, false,
                executionContext, (channel, observer2) -> createConnection(channel, observer2, tcpConfig),
                observer);
    }

    private Single<FilterableStreamingHttpConnection> createConnection(
            final Channel channel, final ConnectionObserver connectionObserver,
            final ReadOnlyTcpClientConfig tcpConfig) {
        return new AlpnChannelSingle(channel,
                new TcpClientChannelInitializer(tcpConfig, connectionObserver, executionContext, false),
                ctx -> { /* SslHandler will automatically start handshake on channelActive */ }).flatMap(protocol -> {
            switch (protocol) {
                case HTTP_1_1:
                    final H1ProtocolConfig h1Config = config.h1Config();
                    assert h1Config != null;
                    return StreamingConnectionFactory.createConnection(channel, executionContext, h1Config, tcpConfig,
                            NoopChannelInitializer.INSTANCE, connectionObserver)
                            .map(conn -> new PipelinedStreamingHttpConnection(conn, h1Config,
                                    reqRespFactoryFunc.apply(HttpProtocolVersion.HTTP_1_1),
                                    config.allowDropTrailersReadFromTransport()));
                case HTTP_2:
                    final H2ProtocolConfig h2Config = config.h2Config();
                    assert h2Config != null;
                    return H2ClientParentConnectionContext.initChannel(channel, executionContext,
                            h2Config, reqRespFactoryFunc.apply(HttpProtocolVersion.HTTP_2_0), tcpConfig.flushStrategy(),
                            tcpConfig.idleTimeoutMs(), tcpConfig.sslConfig(),
                            new H2ClientParentChannelInitializer(h2Config),
                            connectionObserver, config.allowDropTrailersReadFromTransport());
                default:
                    return unknownAlpnProtocol(protocol);
            }
        });
    }

    static Single<FilterableStreamingHttpConnection> unknownAlpnProtocol(final String protocol) {
        return failed(new IllegalStateException("Unknown ALPN protocol negotiated: " + protocol));
    }
}
